This invention relates to a vapor-phase chloro-denitration process for the preparation of nuclear-chlorinated aromatic compounds useful as chemical intermediates.
The preparation of chlorobenzene compounds by chlorodenitration of the corresponding nitrobenzene compounds in the liquid phase is known. For example, the liquid phase chlorodenitration of 2-nitrobenzonitriles to form the corresponding 2-chlorobenzonitriles is disclosed in U.S. Pat. No. 4,225,534. Furthermore, it is known from the chemical literature that certain nitrobenzene or fluoronitrobenzene compounds may react with chlorine in the vapor phase with the replacement of nitro groups by chlorine atoms. (Vorozhtsov et al, Zhurnal Obshchei Khimii, Vol. 31, No. 4, pp. 1222-1226, April, 1961). Such vapor phase reactions have been shown to be feasible only with certain unsubstituted nitrobenzenes or fluoronitrobenzenes. However, it has not heretofore been known or suggested that other substituted nitrobenzenes or substituted fluoronitrobenzenes might undergo chlorodenitration by vapor phase reaction with chlorine. U.S. Pat. No. 4,259,510 discloses a process for the preparation of trifluoromethylphenyl nitrophenylethers utilizing phenol reactants which may be prepared from substituted halobenzene reactants, including dihalobenzotrifluorides. U.S. Pat. No. 4,012,453 discloses a catalyzed oxychlorofluorination reaction of toluene, benzotrichloride, hydrogen fluoride and oxygen wherein the reaction product includes chlorofluorobenzotrifluoride as a component thereof. In addition, the incidental preparation of a chlorofluorobenzotrifluoride is described in Feast et al in J. Chem. Soc. (c), 1971, 1547-49. The reference discloses 4-chloro-3-fluoro-benzotrifluoride as a minor co-product obtained during the synthesis of 3,4-difluorobenzotrifluoride from 3-amino-4-fluorobenzotrifluoride.